Intracranial electroencephalographic approaches in the intensive care unit: Safety, feasibility, and coverage

Nonconvulsive epileptic activity is common after acute brain injury and contributes to neuronal injury and poor outcomes. Although intracranial electroencephalography (iEEG) improves detection compared with surface EEG (suEEG), it currently relies on focal recordings of epileptic dynamics. We prospectively evaluated multielectrode iEEG strategies designed to achieve large-scale cortical and deep brain coverage in critically ill patients.

In a prospective cohort of adults with acute brain injury requiring invasive neuromonitoring, we implemented four depth electrode-based iEEG techniques: three electrocorticographic approaches (open subdural, burr hole subdural, and foramen ovale) and one stereotactic (transcortical) approach. The primary objective was to establish and quantify the extent and durability of cortical recordings. Additional assessments included safety, feasibility, and management impact. Electrode localization was performed in MNI305 space, and recording longevity was assessed using Kaplan-Meier and Cox proportional hazards models.

Thirty patients with severe brain injury underwent implantation of 64 electrodes (772 contacts), yielding 361 total iEEG recording days across heterogeneous etiologies and surgical settings. Multielectrode implantation enabled distributed sampling spanning multilobar frontoparietotemporal cortical clusters. Overall, 72% of electrodes sampled cortical convexity alone, whereas 28% incorporated deep targets, including mesial temporal and orbitofrontal regions. Recording durability differed by implantation strategy (log-rank p = .0002), with a mean combined iEEG-suEEG monitoring duration of 14.5 days per patient. Implantation was successful in >95% of electrodes, monitoring started within 24 h postoperatively in 88%, and the per-electrode risk of a causally related adverse event was 3.1%, without hemorrhagic complications. iEEG influenced treatment initiation or escalation in 32% of monitored patients.

Multielectrode iEEG strategies enable durable, large-scale cortical sampling in acute brain injury while remaining feasible and safe in the intensive care unit. By shifting from focal to distributed spatial sampling, these approaches provide a conceptual framework for improving detection of epileptic activity in critically ill patients.